Brownells is sure a good place to ask.
Most new blued guns,and the process most gunsmiths use,is a hot caustic salts bath.
The salts,tanks,burners,etc are quite an investment to do a couple of guns.
It also may take more than a couple of guns worth of learning curve to get the results you want.
There are some processes that only require a boiling water tank.Likely a 3 burner blind stove will work.The iron tank from Brownells is good.
The part5s are boiling,you lift the parts out,swab them with solution,return to the boil.A coat of fine rust develops.A soft stainless brush is used to card off the rust.
Brownells makes a product for this process to produce a blued finish.I used a Mark Lee muzzle loader browning solution.the results were very good.My finish is tough,looks like very black coffee.It looks like a deep,rich blue job,but instead of a blue-black,it is a brown black.
Good process for levers,single shots,etc.